Intra-aortic balloon pumps (IABP) are used to provide counter pulsation within the aorta of ailing hearts over substantial periods of time, e.g. to provide ventricular assistance during cardiogenic shock, low cardiac output in post operative care, weaning from cardiopulmonary bypass, treatment for refractory unstable angina, and other circumstances of subnormal cardiac function. Such pumps include a large flexible intra-aortic balloon (IAB) which is readily inflatable under low pressure to substantial size and displacement. The balloon is mounted on a catheter device for insertion of the balloon into a remote artery, typically a femoral artery, and through the intervening vascular system of the patient to the aortic pumping site while the balloon is deflated and furled.
An intra-aortic balloon typically is a flexible balloon of substantial size, i.e. on the order of about 0.5" to about 1.0" in diameter when in an inflated but unstretched condition, and about 8" to 12" in length. Typical sizes are of 30 cc, 40 cc and 50 cc displacement. The balloon may be formed of any suitable material, with polyurethene presently being preferred. A hydrophilic coating preferably covers the balloon and forms a lubricous outer surface which is very slippery when wetted by an aqueous fluid, such as blood, while permitting processing and furling of the balloon and handling of the balloon and related pump mechanism in a normal manner when dry. Presently preferred coatings and appropriate modes of applying such coatings are disclosed in co-pending application No. 08/170,513, filed Dec. 20, 1993, the disclosure of which is incorporated herein by this reference.
The balloons are formed of thin films, as by a dip-casting process. One example is a polyether based polyurethene balloon of about 0.003"-0.005" wall thickness formed by dip-molding on an appropriately shaped mandrel, with later addition of a hydrophilic coating as referred to above. One presently preferred embodiment utilizes such balloons with wall thicknesses in the lower end of this range, i.e. 0.003"-0.004". It will be appreciated that the balloons are rather frail from a mechanical standpoint, and can be scratched or torn if not handled carefully and with appropriate safeguards during packaging, shipping and subsequent handling by the health care providers in the course of removal from the packaging in preparation for use.
In the course of manufacture, each balloon is assembled into a catheter assembly, with opposite ends of the balloon being bonded to the distal ends of two coaxial lumens. The balloon also is tightly furled about a distal portion of the inner lumen to facilitate subsequent insertion through a small opening into a patient's vascular system. The subassembly of the lumens and furled balloon then is threaded through a small packaging sheath, with the furled balloon thereby being drawn into the sheath which tightly surrounds the furled balloon section. The sheath remains on the balloon and maintains the balloon in its furled compaction to a minimum effective outside diameter during sterilization, packaging, shipping and handling, up to the place and time of insertion into the patient. While in its sheath, the furled balloon also typically is heated, e.g. to a temperature on the order of about 135.degree. F. for about 12-16 hours, to assist in setting and thereby sustaining the furling during insertion following removal from the packaging sheath by the user.
Each sheath unit typically has been an extruded plastic tube, often with a substantial end-section affixed to one end of the tube as by being bonded or molded thereonto. The end section is of substantial size and body to provide a convenient means for gripping, handling and restraining the sheath unit against the forces of insertion and removal of the catheter balloon section. The end section also forms a graduated or flared inlet to assist in guiding the furled balloon section into the tube. The opposite or removal end of the tube often has been simply the square cut end formed during guillotine severance of the respective sheath tube from an indeterminate length of such tubing.
At the point of use, the balloon section is withdrawn from its packaging sheath by the health care user. It will be appreciated that this withdrawal may occur under conditions of stress and time urgency, by a wide variety of personnel.
In all events, it is desirable to provide a high degree of protection and assurance against scratching, abrasion or other damage to the balloon in the course of its insertion into and subsequent removal from the packaging sheath.
It is an object of this invention to provide improved packaging sheaths for intra-aortic balloon catheters.
It is a more specific object of this invention to provide such sheaths which reduce or avoid risks of scratching, abrasion or other damage to the balloon in the course of its insertion into the packaging sheath.
It is yet another object of this invention to provide such packaging sheaths of designs which reduce or avoid the risk of scratching, abrasion or other damage to the balloon in the course of its removal from the packaging sheath.